As a related-art bearing device for a wheel, for example, there is proposed a bearing device for a wheel, which is configured so that a hub wheel is separable from an outer joint member of a constant velocity universal joint to attain excellent maintainability (see, for example, Patent Literature 1). As illustrated in FIG. 14, the bearing device for a wheel as described in Patent Literature 1 includes, as main components thereof, a fixed type constant velocity universal joint 106, and a bearing 120 for a wheel including a hub wheel 101, an inner ring 102, double-row rolling elements 103 and 104, and an outer ring 105. In the bearing device for a wheel, a stem section 130 of an outer joint member 124 of the fixed type constant velocity universal joint 106 is press-fitted into a shaft hole 138 of the hub wheel 101. Further, a bolt 142 is inserted from an outboard side (left side in FIG. 14) through a bolt insertion hole 146 of the hub wheel 101, and the bolt 142 is threadedly engaged into a bolt hole 141 formed in an end portion of the stem section 130 on the outboard side. In this manner, the outer joint member 124 and the hub wheel 101 are fixed to each other.
In the above-mentioned bearing device for a wheel, as illustrated in FIG. 15 and FIG. 16, when the stem section 130 of the outer joint member 124 is press-fitted into the shaft hole 138 of the hub wheel 101, convex portions 137 of the stem section 130 of the outer joint member 124 are transferred onto an inner peripheral surface of the shaft hole 138 of the hub wheel 101. In this manner, concave portions 140 that are held in close contact with the convex portions 137 with interferences are formed in the inner peripheral surface of the shaft hole 138 of the hub wheel 101, and there is defined a convex and concave fitting structure in which the convex portions 137 and the concave portions 140 are held in close contact with each other in an entire range of a fitting portion therebetween. Thus, the outer joint member 124 and the hub wheel 101 are coupled to each other so as to allow torque transmission therebetween. At this time, as illustrated in FIG. 15, before the convex portions 137 are press-fitted into the shaft hole 138 of the hub wheel 101, the inner peripheral surface of the shaft hole 138 exhibits a simple cylindrical portion 139 having no female spline. Accordingly, when the stem section 130 of the outer joint member 124 is press-fitted into the shaft hole 138 of the hub wheel 101, in order to transfer the convex portions 137 of the stem section 130 onto the inner peripheral surface of the shaft hole 138, a large press-fitting load is needed, and it is necessary to use a pressing machine or the like.
In this context, in a configuration described in Patent Literature 2, as illustrated in FIG. 17, a plurality of convex portions 237 are formed on an outer periphery of a stem section 230 of an outer joint member 224 to extend in an axial direction, and a plurality of small concave portions 239 are formed in advance in a shaft hole 238 of a hub wheel 201 to extend in the axial direction. The plurality of small concave portions 239 have interferences with the convex portions 237. Further, as illustrated in FIG. 18, the stem section 230 of the outer joint member 224 is press-fitted into the shaft hole 238 of the hub wheel 201, thereby forming concave portions 240 onto which profiles of the convex portions 237 are transferred. Thus, there is defined a convex and concave fitting structure in which the convex portions 237 and the concave portions 240 are held in close contact with each other in an entire range of a fitting portion therebetween. As described above, the small concave portions 239 are formed in advance in the shaft hole 238 of the hub wheel 201 so that a load applied when press-fitting the stem section of the outer joint member into the shaft hole of the hub wheel can be reduced as compared to a case of transferring the convex portions 137 onto the simple cylindrical portion 139 as illustrated in FIG. 16. Therefore, when the outer joint member is press-fitted into the hub wheel of the bearing for a wheel, there is no need to separably prepare a dedicated jig. With the screw fastening structure constructed by the bolt 142 and the bolt hole 141 that are components of the bearing device for a wheel, the constant velocity universal joint can be easily coupled to the bearing for a wheel.